Pulse width memory units



ll/A

*Ja-15.3"v

37 G n y PYLNVL i@ 2X 40) T /s' I- 347 kif May 19, 1959 FJ. E E

l INVENToR Gelarye G'ree/Ie.

United States Patent O 2,887,674 PULSE vwIDrrrimsMoRv UNITS "j George-B. Greene, BerkeleyyCalif., assignor to Marchant I. j n Research, Inc., a corporation of California vApplicnnm May 14, -19ss,serial No. 355,115 l. v zz claims. (o1. :14o- 174)V The present invention ,concerns digital computers, and more Vparticularly relates to a variable pulse width memory systenrfor such computers.

ABy virtue of -the inherent on or oi, or 1, character-I istics of present-day computingequipment, most digitalv computers operate either in the binary system or in some modification thereof. These computers Aoften employ a memory unit for storingv large quantities of digital in formation, one` typey of memory unit comprising a mag netic medium, such as-a magnetizable tape. The medium may-` be moved relative to al-writing transducer which magnetizes successive areas, or cells of the medium in either of two modes for representing the respective `binary values O and ll; Y.A medium which has been magnetized may be moved relative to a reading `transducer which responds tothefrecorded information 'by producing a signal that is the Afirst 'derivative otl the signal employed for writing. n i

In the prior art, there-are two-principal systems of magnetizingfa medium to representbinary information. The first such system is known as the restore-to-zero system, in which therbinaryvalue 1 may be representedby a positive pulse (magnetizing `the medium to a first, or positive saturated state), and the binary value 0 is representdwby a` negativepulse (magnetizing the4 medium to a second, 'or negative'saturated state); The areaon the surface `ofthe `medium between digits is unsaturated for writing lare f all offsubstantially the `sanne width, so that the' amplifying circuits" employed inconjnnction with the memoryunit needmothave broadband characteristics and may;` thereforeybe of comparatively simple design; and (2) the'reis` no necessity to provide an auxiliaryclock pluse `system-for isynchronizingthe computer, since the leading or trailing edge of the-magnetized area'lin `each cell lmay -be 'employedu for this purposei The second'principalV system employed for magnetically e recording `'digitaleinforifiation is known'as `the non-restore system inwhich, again, a positive state of saturation of an area `onlthetmedium represents a` 1, and a negative state Aof saturation represents a 0, butin which ther'eare no areas of'lnonsaturation. Contiguous cells whichre'present thel-samevalue 0 or 1 have no-bou'ndary between them, V`i.e.', they"constituteratregion of saturation which "isicontinuous until Vther recorded value changes` from Oto 1l or viceversa In the non-restore system,l the readout signal, being the first derivative of the writing signal, comprises a positive pulse when the recorded 2,887 ,674 Patternedr May 19, `1959 ICC . 2` valuechangesffrom .v0 to 1; and a negativepulse when the recorded value changes from 1 to 0. Since an in-` definite number of Ofs orl ls mayfbe stored-in a continuous series, there'is no'regularity in the timespacing Hof the` readout signals. Therefore'this' systemhas no selfclocking property, and auxiliary means -mustlbe providedI 4for synchronizing the recordedinformation `with other -units of the computer. liurthermormY since the width of the recording pulses dependsentirelyupon-the numberofy consecutive .l's'or- 0s that are-to'be recorded, the amplifying circuits employed in conjunction withthe memory' unitmust lbe capable-of handling pulses which vary' in width from a single cell to a large 'number of cells;l Inf the non-restore system, however, since there are no regions of nonsaturationof 'the medium, there is no need forerasingequipment.

The -presenteinvention 'employs `a' recording system` whichcombines-the advantagesfof the restore-to-zero andthe non-restoref-systemsfand :eliminates the unde-l sirablefeaturesl of both; Each digitisrepresented by 'anf individual magnetized area of the medium, thereby `providing -a self-clocking property, Abut lthereare no areas: of the medium which "are unsaturated, so thatno erasing-` equipmentisnecessary.` In the' present system the mediumv is normally saturated in' a rst state, forexample;` negative.v

In each cell,` a digit 0 or lt'isy stored by'saturatingtheL medium 1vin `a second -state, Vfor *example* positive, th'ey distinctionbetweena 0 and al beingthe timeof dwellI in the second state ofsaturation.` -Before'the end of any` cell, whether it contains a 0 ora 1, the medium `is r'e turned to its first state of saturation. Therefore,` a sepa# rate pulse is employedffor-writing.eachdigit, 'and l*the widths of thetwo kinds `-of Writing pulses do not' differ great1y,eso that broad band amplification is no't require"d.fl

Although numerous otherl arrangements willbe obvious: to thoseeskilled -in the art, the presentfinventionwill'be described in-relationfto` a medium wherein-allot the@ cells are of the same size, and whereinthereiisnozspace' between consecutive cells. Either aO orfl" is writtenby reversing the -stateofr magnetizationV ofA thefmedium at the leading-edge` ofthe corresponding cell: 1 To"y complete the=writing1of a 0 in'a cell, the state of magnetization? is again reversedfafter approximately "-two thirds of the cell has passedfthe'writing head', while to 'complete the writing offa 1, theestateof the'cell is reversed afterdapproximatelyf one-third of thetcell hasfpassedthe writing head. A stored 0 and a storedel maybe illustrated by the respective waveforms Ashownfi'n Fig. 1 to the right 'of unitsfPGo and PGI, Vto bedescribed hereinafter.

Each full wave form thus repres'ents` `a complete'cell, and

the" highlevelsirepresent"the-respective dwells of re-v versed magnetization `for a Oand al.'

It isl therefore a'principal object of thpresent invention` to magnetically recorda pluralityfof `dilferent items of information-by magnetizingza respective area of uniquesize, on a magnetizable medium, to correspondv to each items' It is a-'imore particular objectof the invention toemagf1 netically record Vbinary informa-tion'onfamagnetic medium by magnetizingan area of a first size on` the mediuml to' s represent a 0 and an areaof a second size to represent Further objects `of the invention are:

To drive a magnetic recording head with pulsesof two widths 4to represent the 'respective binary 'values 0 to 1: Toread out from a magnetic medium vinformation re corded as magnetized areas"offa pluralityiof-sizesto represent a corresponding'plui'ality of items'of 'informationrft L L.

To readout-from-a magnetic medium information recorded-as magnetized areas of two sizes to represent the binary values 0 and l.

To provide a self-clocking magnetic recording system wherein a medium is magnetized in either of two saturated states with no unsaturated dwells.

To representbinary information ,in successive cells of a magnetizied mediunr wherein there are ne unsaturated dwells.

The underlying principles of the present invention are therefore the magnetization and detection of af magnetic medium in areas of a plurality of sizes to represent a corresponding plurality of items of information.

Other objects and principles of the present invention will appear from following description, reference being made to the drawing in which:

Fig. l is a block diagram of a writing.' circuit embodying the present invention, and

Fig. 2 is a block diagram of a reading circuit embodying the present invention.

Writing circ'ut The writing circuit of the presentiv invention comprisesa timing pulse input and avalue selector which gates the timing'pulses into a 0v channel; or! a 1l channel,- according to the value of the digitlto bewritt'e'n.. In either channel, each timing pulse triggers a pulse generator' which produces a square writing pulse-'ofa' predetermine'dl width, the` writing pulses generatedin the O-'clannel being, for example, twice the width of? thefwritng'puls'es'generated in the 1 channel. The writingpulses'f'rom'both channels are amplified and fed to a magnetici transducer or writing: head, in such manner' that' the head# is always energized in one or the other of two" oppositedirections. A medium movingiadjace'nti the head is? saturated by the head in a first direction for the/duration of each or l writing pulse, and is saturated inthe' opposite direction at all other times.

Referring to Fig. l, atrigger circuit is employed to control the gating of timing'pulses from an-nput terminal to either aOJch'annelor al channel, according to the value of a digitv which is to be recorded.

'Ihe trigger circuit 10 has two:v stable states of' operation, designated the 0 state and the" 1 state,and is set' for eachV digit tothe appropriate'foneA ofits two states by a pulse; on either a Os bus 11 ora lrsbus 12. A gate G0, whichis connected. to the trigger circuit 10 by a control lead. 13, is armedvwhen the trigger circuit is in its 0 state. control lead 14' whenv the triggercircuit'is in its 1 state. The trigger circuit- 10, and-eachgate Go andGl, may be ofthetypesA shown inFigs. l and3, respectively, of the copending' applicationSerial No; 344;()25, led March 23, 1953, by G. B. Greene.

A positive timingI pulse isi received at input terminal 15 following the selection of each digit on trigger circuit 10. Each timingpulse interrogates both gates G0 and G1 and is passed'through' one or theother'of these gates, according to the digit selectio'rnto produce a negative pulse in the-related 0 channel or l channel.

Al negative pulse inthe O channel ktriggers a pulse generator PGU which produces a relativelyv wide square positivepulse on ai lead 16,..wh`ilea pulseinthe 1 channel triggers a pulse generator PG1 which produces a relatively narrow squarepositive pulsezonafle'ad 17 For purposes of illustration, it will be' assumed thatth'ec interval between timing pulses at terminal. 15"is l2 microseconds and that the width of the square pulses generated by PGO'V and PG1 are 8 microseconds and 4 microseconds, respectively. The unitsPG, and PG1 may be'any 'of the severalwell-kuown` types of square pulse generators'such, for example, as shown -in1' `igs.` 512.on pg 170 of Waveormsj? vol. 19, M'.I.T. Radiation Laboratory Series, McGraw-HilL. New York', 1949:

v Thefoutput leads 16 landwll from-PG0wand PG1. are joined to form a single input lead 18 to a phase inverter 20;;l The phase inverter mam-for examplegncomprise a triode ampliier. with' anode? and1cathode'fresistors, and

Similarly, a gate-G1- is. armed through a' having a grid input from lead 18, an anode output to a lead 21, and a cathode output to a lead 22, or it may comprise simply a pulse transformer wherein leads 21 and 22 constitute output leads from opposite sides of the secondary winding.

Each positive pulse input to the phase inverter 20, from either PGD or PGI, is amplilied to produce on the output lead 21 a negative pulse of the same Width as the input pulse, and on the output lead 22 a positive pulse of the same width as the input pulse. The positive pulse output on lead 22 may be related tov an appropriate reference potential and treated as a negative pulse of a width which is the complement of the width of Athe negative pulse on lead 21. For example, when the phase inverter 20 receives a 0 pulse (8 microseconds wide) for PGD, its output on lead 21 is an 8 microsecond negative pulse at the beginning of the l2 microsecond digit interval. The 8 microsecond positive pulse on lead Z2 may be treated as the reference potential and the remaining 4 microseconds in the digit interval may be treated as a 4 microsecond negative pulse. Therefore, during each digit interval, there is an output from the phase inverter 20 comprising either an 8 microsecond or a 4 microsecond negative pulse on lead 21, followed by a corresponding 4 microsecond or 8 microsecond negative pulse on lead 22. The shapes of the above-described complementary pulse pairs are shown in Fig. l adjacent leads 21 and 22.

The pulses on leads 21 and 22 are amplied and inverted by a pair of amplifiers 23 and 24, and then feed to opposite sides of an energizing coil 25 of a writing head Z6. A magnetic medium Z7 is moved adjacent av gap 28 on the writing head and is magnetized to saturation in one or the other of two opposite directions, ac cording to the direction of current through the coil 25. It will be seen that the medium is saturated in a first direction for either 8 or 4 microseconds at the beginning of each digit interval by a pulse from amplifier 23 representing either a O or a l, respectively, and that it is saturated in the opposite direction for the remaining 4 or 8 microseconds of each digit interval.

Reading circuit The reading circuit comprises a magnetic reading head adjacent the moving medium, a gate which is opened for a predetermined interval by a circuit whichl responds to the leading'edge of each area of the medium representing a recorded digit, and a circuit which interrogates the gate in response to the trailing'edge of each such area. The gate is kept armed,- in response'to each digit, for an interval long enough to receive and pass the trailing edge signal from a recorded digit l, but not long enough to pass the corresponding signal from arecorded digit 0.

Referringto Fig. 2, the reading head 28a is located ad jacent the medium 27 and may be either the head em ployed for writing'or a separate head.

As each area of positive saturation, i.e., each recorded digit, on the medium passes adjacent the reading head, it induces on'a reading coil 25a a signal which is the irst derivative of the signal employed for writing the digit. Since each digit 0 or 1 is Written with aA square positive pulse, the output signal from coil 25a in re sponse to each digit comprises a leading positive pulse and a trailing negative pulse, as shown in Fig. 2. The spacing between the leading pulse and the trailingr pulse depends upon whether the corresponding digit is 0 or l. If it is 0, the spacing between these pulses is, in the present example, 8` microseconds, whereas if it is a l, the spacing-between pulses is 4 microseconds.

The output from coil 25a is connected by a pair of leads 30 and 31 to a class B or class C amplifier 32 which amplies only the positive leading pulse of each digit pair and therefore produces a negative output pulse in response to the leading edge of each digit. Each output pulse from amplifier 32 is fed'by a pair of leads 33 and 34"@ kn output terminal'35 and may beeniployed there to drive a timing pulse generator for synchronizing-.the reading and writing circuits and/or other computer elements. For example, the output pulse fromfterminal 35 may be feduthroughva suitablepulse polarity inverterl (not shown) to the input terminal (Fig. l) offthe writing circuit thereby providing a self-clockingsystem.

Each output pulse from amplier 32 is also appliedwbyV lead 33.to a pulse generator PGg, which is similar to pulse generators PGO and PG1 described in relation11V to Fig. l. In response to each pulse on lead 33, pulse generator PGLL, produces a square pulse which arms a gate G2` through `a control lead 36. Gate G2 is similar` to gates Goiand G1 described in relationito Fig. Land is armed only for the'duration of each pulsefrom PG2. i In thepresenty example, the square pulses from PG'Z arel 6 microseconds wide for reasons described below.

EachIpositive andnegative pulse pair fromcoilA a is fed throughlead to a second channelcomprising a class A amplifier 37 and a lead38 for interrogating gate- G2. Amplifier 37 invertsevery pulse, so` that each digit is represented on lead 38 by a leading negative pulse anda trailing positive pulse. The leading negative pulseV in each digit pair has no effect on gate G2, but the trailing positive pulse is passed by gate G2 if that gate-is armed.

Since.y gate G2 is armed in coincidencewith the leading` pulse of each digit pair and remains armed for 6 micro-l" seconds,` and since the trailing pulses for the digits 0 and l follow'the leading pulses by 8 and 4 microseconds,

respectively, it will be seenthat the trailing pulse for` each digit l is passed by gateGz, whereas the correspondingrpulse for each digit 0 arrives at gate G5 after theY latter is Jclosed; Therefore, the output `signal from i gate G2, which is fedrby a lead 40 to an output'terminal 41,V

comprises anegative pulse `correspondingto each `digit l, whilethere is no pulse outputfrom gate 'G2.correspond ing to any digitO.

It will be apparentifromthe foregoing description of the illustrative writing `and reading circuits that'the vention is notlimitedto the binary system.v A separate v4() diiferent'items of informationfso that the writing circuit l pulse'width may beassigned to each of any number of (Fig.` 1) may, for example, have in channels `representing the`various vdigits of the'radiX `n, or there may be additional channelsyeach assigned "a'unique pulse `width,"for representing control functions ortalphabetical `indicia rathenthan digits. In such casethe readingfcircuitV (Fig.5y 2) need 'not include gate G2 and its controls, thel differ-"r ent .items ofinformation being identified by the time spacing betweentherpulsevpairs at the output of ampliiier 37." Alternatively, amplifier 37 may be followed by a class.B or C ampliiierso that only the trailing edge signals `appear at the output terminal 41, and these'signals may be identified bya from terminal 35.

I claim: 1. In a computer `having a moving magnetizable medium, thetcombination of means fornormally magtime comparison with signals netizing the medium to saturation `in a first direction of" magnetic polarity; information input means for` producing signals representative of .unique items of information; and transducing means coupledto the 'input means `and operable in response to the occurrence of a signal, representative of a given item of information, for magnetizing the medium to saturation in a second direction of maga 'netic polarity` during a time interval having a duration uniquely corresponding to the given item of information.

2. In a computer having `amagnetizatble medium, the combination of:r means for normally magnetizing the medium to saturation `in a first direction of magnetic pol-arity'g n information channels, each` channel being adapted'to receive a signal representing a unique item" of information,i information `input means for' transmitting signals to said channels,land a recording 4circuit operable in response to receipt of a signal by a given channel for magnetizingan areaof the medium to saturationin a second direction of ymagnetic polarity, the size 'of said area being/uniquely corresponding to said given channel:

3. In a computer, the-combination of:` a moving mag-".1 netizable medium; Vanenergizable transducer disposed in" cooperative relation 'with-the medium; means for normal# ly energizing the transducer in a rstdirection of polarity; information input means for producing signals representative of unique" itemsof information; -andfan energizingl. circuit coupling theinput means to the transducerand operable in response to a signal representing agiven item v of information to energize the transducer in a directionlofpolarity opposite to-said rst direction of polarity for a time `interval havingfa duration uniquely" corre` sponding to said given item of information.v

4. In a computer wherein digital information is represented lbya series of pulses, the combination of:af0 channel and a lchannel, means for pulsingthe 0 channel toirepresent the digiti), means for pulsingthe 1 channel :for representing Ythe digit; l, a transducer, a circuit inter connecting the 0 and'l channels andthe transducervfor normally energizing the transducer in a first directionof i polarity and for energizing the transducer in a direction ofpolarity opposite to said first direction of polarity forl a first duration in response to each' pulse in the O channel i `1and for a second duration in response' to eachpulsein` the 1 channel, anda recording medium disposed in co' operative relationship with the transducer and upon which' the transducer records asignal in response 'toeach energization` of the transducer.

sented by a series of pulses; the combination of, a 0

channeland a 1 channel, means for pulsing theO channel to representthe digit 0, means for pulsing the l channel to represent the digit 1, a respective pulse generatorin each of saidchannels operable in response to a pulsefin the -related channel` for/generating a square pulseof a unique width corresponding to the Vrespective channel, 'a

magnetic Writing transducer," a4 magnetizable medium moving adjacent to said transducer, and a circuitfinterf connecting the pulse generators and the transducerrto f energizethe latter 'for magnetizing the medium to-satura-` tion-in a first direction` of magnetic polarityv during the1 absence of a pulsefrom either pulse generatorand to saturation'in a direction of magnetic polarity opposite to' `said first direction of magneticpolarity for the-duration of each pulse from a pulse generator.

energize said transducer in a direction of polarity opposite to said iirst direction of polarity for the duration of said recording signal.

7. In a magnetic recording information in a series of along a recording track of system for storing binary equal-sized contiguous cells a moving magnetic medium,

the combination of: a transducer disposed in cooperative relation with the medium; means for normally energizing Athe transducer in a first polarity; information input means for receiving a signal representative of an item of information; an energizing circuit controlled Ibysaid input means and operable to reverse the direction of energization of said transducer for magnetizing a iirst portion of said cell" ,in a polarity opposite to said rst polarity, said iii-st porl corresponding tion of said cell having a length uniquely to said item of information.

8. In a'computer including a moving medium having' successive areas thereon in a predetermined state of mag` netization to represent respective numeral values whereby 5. In a computer wherein digital information is reprethe leading edges of said areas in the direction of movement of the medium are regularly spaced, and the trailing edge of a given area is spaced from the leading edge of the given area by either a first distance to represent a first numeral value or by a second distance to represent a second numeral value, the combination of: a reading transducer disposed adjacent the path of the mediumY and operable to produce a first readout signal in response to the movement adjacent the transducer of the leading edge of each area and a second readout signal in response to the movement adjacent the transducer of the trailing edge of each area; gating means connected to receive the signals from said transducer; and gate control means responsive to said first readout signal for controlling said gating means to produce an output signal from said gating means only in response to the second readout signals derived from areas representing said first numeral values.V

9. In a computer including a moving 'magnetizable medium having successive areas thereof in predetermined states of magnetization to represent items of information; the length of each area along the direction of movement of the medium being uniquely related to an item of infomation represented by said area, the combination of: a reading transducer disposed adjacent the path of the medium and energized to produce a pulse of first polarity in response to the movement adjacent the transducer of the leading edge of each of said areas and a pulse of opposite polarity in response to the movement adjacent the transducer of the trailing edge of each of said areas; a gate connected to receive the output of said transducer; and gate control means connected to the output of said transducer and having an arming connection to said gate, said gate control means operative onreceipt of said pulse of first polarity to arm said gate for a predetermined period whereby an output signal is developed when said pulse of opposite polarity is received by said gate within said predetermined period. I

l0. In a computer including a moving medium having successive areas thereon in a predetermined state of magnetization to represent respective numeral values whereby the leading edges of said areas in the direction of movement of the medium are regularly spaced, and the trailing edge of a given area is spaced from the leading edge of the given area by either a first distance to represent a first numeral value or by a second distance to represent a second numeral value, the combination of: a reading transducer disposed adjacent the path of the medium and operable to produce a readout signal in response to the movement adjacent the transducer of each leading and each trailing edge of each area; a normally closed gate having an interrogating input coupled to the transducer; means coupled to the transducer for arming the gate in response to the first readout signal from the transducer in each pair of signals related to a given area of the medium; and means for maintaining the gate armed for a predetermined time interval.

11. In a computer including a moving magnetizable medium having successive areas thereof in a predetermined state of magnetization to represent items of information, tlielength of each area along the direction of movement of the medium being uniquely related to an item of information represented by said area, the combination of: a reading transducer disposed adjacent the path of the medium and operable to produce a first readout signal in response to the movement adjacent the transducer of the leading edge of each area and a second readout signal in response to the movement adjacent the transducer of the trailing edge of each area; lgating means connected to receive the output of said transducer; and gate control means responsive to first readout signals for controlling said gating means to produce an output signal from said gating means only in response to second readoutsignals derived from areas having a length less than a predetermine'd length.

l2. In a magnetic storage system, the combination of: a moving magnetizable medium; a writing circuit for recording bits of information in a series of equal-sized contiguous cells along a recording track of said medium, said writing circuit comprising, a transducer disposed in cooperative relation with said medium, means for normally energizing said transducer in a first polarity, information input means for receiving a signal representative of an item of information, a timing input for receiving timing pulses, an energizing circuit jointly controlled by said information input means and said timing pulses and operable to' reverse the direction of energization of said transducer for 'magnetizing a first portion of said cell in a polarity opposite to said first polarity, the length of said first portion uniquely corresponding to said item of information; a. reading circuit including reading means for detecting said magnetized cell and operable to produce a first readout signal in response to the detection of the leading edge of said first portion of said cell and a second readout signal in response to the detection of the trailing edge of said first portion of said cell, a first output circuit coupled to said reading means and conditioned by said first readout signal to produce a manifestation representative of said item of information upon receipt of said second readout signal, a second output circuit coupled to said reading means and operable to produce a timing pulse in response to the receipt of said first readout signal, and a connection for applying said timing pulse to said timing input of said writing circuit.

13. An information recording system comprising: timing signal input means; information signal input means; a plurality of normally closed gates each corresponding to a different item of information and each connected to said timing signal input means; gate arming means connected to said information signal input means for arming the gate corresponding to the item of information to be recorded; a respective pulse generator connected to the output of each of said gates and operable upon receipt of a timing signal from said gate for generating a pulse whose duration is uniquely related to said item of information; a moving storage medium; means connected to said pulse generators and operable in response to a pulse from said pulse generators for energizing said medium in a predetermined sense for the duration of said pulse.

14. In an information storage system having information stored in a series of equal sized contiguous cells along a recording track of a moving storage medium, the first portion of each cell energized in a given polarity for a distinctive length to represent respective items of information and the remaining portion of each cell energized in opposite polarity, the combination of: a transducer disposed adjacent the path of the medium and operable to produce a first signal in response to the movement adjacent the transducer of the leading edge of said first portion of each cell and a second signal in response to the movement adjacent the transducer of the trailing edge of said first portion of each cell; a normally closed output channel connected to said transducer and operable to give an output in response to the receipt of said second signal when said channel is open; and means connected to said transducer and responsive to said first signal for openig said output channel for a predetermined interval.

15. In an information storage system, the combination of: a storage medium having a series of equal-length contiguous cells, a first portion of each cell being in a first predetermined state and having a distinctive length to represent respective items of information, the remaining portion of each cell being in a second predetermined state; a transducer disposed adjacent the medium, said transducer and said medium being arranged for relative motion and said transducer operable to produce a first readout signal in response to the lleading edge of said first portion of each cell and a second readout signal in response to the trailing edge of said first portion of each 9; Cell; and. an Output Cireutfor. waiving Saidnreadgut Signals and .Operable .tontqdyse angutput Sisaalnly in rpnseto the reeintnf Saidiirstand 'Second .readout sisnalsina predetermined.timefrelationshin 16- In. an information Staragesystem, the comin-uien of: a moving magnetic me having a seriesofequallength .contiguous cells. a rstnortion of .each cellbeins masetizedV `in a predetermined. rolarityyand having. .a distinctive ,length s to represent;A aY respective itcm3 0f :IIQI': mation, the remaining portion of each cell being magnetized in the opposite polarity; a transducer disposed adjacent the path of the medium and operable to produce a pulse of first polarity in response to the movement adjacent the transducer of the leading edge of said iirst portion of each cell and a pulse of opposite polarity in response to the movement adjacent the transducer of the trailing edge of said first portion of each cell; a rst output circuit coupled to said transducer and operable to produce an output signal only in response to each pulse of first polarity; and a second output circuit coupled to said transducer and conditioned by each pulse of rst polarity to produce an output signal upon receipt of a pulse of opposite polarity within a predetermined interval.

17. An information recording system comprising: a moving energizable medium; timing signal input means; information signal input means; pulse generating means connected -to said information signal input means and said timing signal input means for generating pulses, the leading edge of each of which occurs in timed relation to a timing signal and the duration of each of which is uniquely related to an information signal; and recording means connected to said pulse generating means and operable in response to a generated pulse to energize saidrmoving medium in a rst predetermined sense for a time interval uniquely related to the duration of said generated pulse and then operable to energize said moving medium in a second predetermined sense for a time interval corresponding to the time difference between the interval between timing signals and the duration of the immediately preceding time interval of energization of the medi-um in the rst predetermined sense.

18. An information recording system comprising: a moving magnetizable medium; timing signal input means; a plurality of information input channels, each channel being adapted to receive a signal representing a diterent and unique item of information; information input means connected to said timing signal input means for transmitting information signals to said channels in a timed relation to the timing signals; means for normally magnetizing the medium in a iirst sense; and recording means operable in response to the receipt of an item of information by a given channel to magnetize an area of said moving medium in a second sense, the area so magnetized being uniquely related to said given channel.

19. A magnetic recording and reproducing system comprising: a moving magnetizable medium; a timing signal input; information signal input means; pulse generating means connected to said timing signal input and said information signal input means for generating, in response to each information signal and in a timed relationship to the timing signals, a pulse whose duration is uniquely related to the information signal; recording means connected to said pulse generating means for normally magnetizing said medium in a first sense and operable in response to each of said pulses to magnetize in a second sense a portion of said medium whose area is uniquely related to said generated pulse; reproducing means disposed adjacent said medium and operable in response to changes in the magnetic sense of said medium to generate pulses, the polarity of which indicates the direction in which the magnetic sense of said medium changes; an output circuit having an enabled and disabled state; gating means connected to said reproducing means for normally maintaining said output circuit in one of its states and operable uponftheisequential receipt of a pulse having ai first.' predetermined polarity followed at` a predetermined:

interval by .La pulse. having a second `.predetermined polarity signalzin response to.` the"v generation; by said second transduing. means. of` 'ar .pulse having a given polarity; and va connection for applying said timing signal tosaid timing.

signal input. Y Y

20. Anlinform'atiorr storage system comprising: a moving storage mediumglar timing signal inputg information signal inpu'trneans; pulse generatingmeans connected to saidy tirriingsignal inputl and said information signal input means for generating pulses whose leading edges occur in timed relationship to said timing signals and of duration uniquely related to said information signals; recording means connected to said pulse generating means and operable in response to a generated pulse to energize said medium in a iirst predetermined sense for a time interval uniquely related to the duration of said generated pulse and then operable to energize said medium in a second sense for a time interval corresponding to the time difference between (l) the time interval between timing signals and (2) the duration of the immediately preceding time interval of energization of the medium in the first predetermined sense; reproducing means disposed adjacent said medium and operable to generate a pulse upon each change in the sense of energization of said medium; an output circuit; gating means connected to said output circuit and said reproducing means and operable to cause said output circuit to produce an output signal only upon the sequential receipt from said reproducing means of a tirst pulse having a rst predetermined polarity and a second pulse having a second predetermined polarity in a predetermined time relationship; timing signal generating means connected to said reproducing means and operable in response to the receipt from said reproducing means of a pulse having a given polarity to generate a timing signal; and a connection for applying said timing signal to said timing signal input.

21. In a storage system, the combination of: a storage medium; a writing circuit for recording bits of information in a series of equal-sized contiguous storage cells along a recording track of said medium, said writing circuit comprising, a transducer disposed in cooperative relation with said medium, means for normally energizing said transducer in a first polarity, information input means for receiving a signal representative of an item of information, a timing input for receiving timing pulses, an energizing circuit jointly controlled by said information input means and said timing pulses and operable to reverse the direction of energization of said transducer for a time interval uniquely corresponding to said item of infomation; a reading circuit including, rst means for detecting a storage cell and for producing a manifestation representative of the item of information contained in said cell, second means for producing a timing pulse upon detection of each storage cell, and a connection for applying said timing pulse to said timing input of said writing circuit.

22. In an information storage system, the combination of: a magnetizable medium; a timing input for receiving timing signals; information signal input means; pulse generating means connected to said timing input and said information signal input means for generating pulses the leading edge of each of which occurs in timed relation to the timing signal and the duration of each of which is uniquely related to an information signal; recording means connected to said pulse generating means and operable in response to a generated pulse to magnetize said moving medium in a first predetermined sense for a time interval uniquely related to the duration of said generated pulse and then operable to magnetize said moving medium in a second predetermined sense for a time interval corresponding to the difference between the interval between timing signals and the duration of the mme'di tely preceding time interv'a'l of magnetization f the me'- dium in the rst predetermined sense; means for detecting changes in the magnetic sens of said medium; means for developing a timing signal upon the detection of a change from said second to said first magnetic sense; and a connection for applying said timing signal to s'id timing input.

References Cited in the le of this patent UNITED STATES PATENTS 1,695,840 Chauveau Dee. 1,8, 192s 12 Hershey July 31, 1934 Byrnes Oct. 5, 1937 Higgitt et al. Sept. 27, 1938 vCohen et al. Feb. 6, 1951 Fleming Mar. 31, 1953 Kaye Nov. 10, 1953 Canfora Nov. 10, 1953 Gates et al. Oct. 25, 1955 Williams Feb. 7, 1956 

